I suspect that until you can prove that you can actually write code, nobody is going to be interested in your services. It is going to be very difficult for you to find work without proof.
Some clients who hire developers don't want their work product being shown to others; I would think this is the rule actually for most clients. At best you can just use their name and say "I worked on building this project ABC at client XYZ". That's why Google etc wants a face-to-face interview or at least over Skype so they can ask you their infamous programmer's questions on the spot. But the OP is making an interesting proposal: if you don't like my work, don't pay me. Haven't seen that before.